I asked my smith this when I got my new m70 classic fetherwt in 280 rem. He worked for both Colt and High Standard? when in Conneticut. He also placed in national NRA competition. On the question he srugged his sholders shook his head and said, If you feel the need clean every five or 10 rounds with hoppes bench rest. He is not fond of the high ammonia cleaners. Bench rest is fairly low ammonia. He said don't let copper build up at any time through the life of a barrel. After what I considered break in, several hundred rounds of various different bullets and loads with dismal results I landed on 57g 4831 with 160 nozler partition, well under 1 moa. So in my experience it is the load that matters. My 7MM mag custom and the 280 will scatter 150 corelockts factory loads.